﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ProjectEulerSolutions
{
    /*
     * 
     * 
     * Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows:

21 22 23 24 25
20  7  8  9 10
19  6  1  2 11
18  5  4  3 12
17 16 15 14 13

It can be verified that the sum of the numbers on the diagonals is 101.

What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed in the same way?

     * 
     * 
     * */
    class Problem28
    {
        public static string Calculate()
        {
            int limit = 1003;

            long count = 1;
            int iterator = 1;

            for (int i = 3; i < limit; i += 2)
            {
                iterator += i - 1;
                count += iterator;
                iterator += i - 1;
                count += iterator;
                iterator += i - 1;
                count += iterator;
                iterator += i - 1;
                count += iterator;
            }

            return count.ToString();
        }
    }
}
